1. Field of the Invention
The disclosure relates generally to AF systems and methods, and, more particularly to systems and methods that determine the position of an AF lens, and anti-dazzling screens thereof.
2. Description of the Related Art
Recently, digital cameras with image sensors such as charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS) have gradually replaced conventional film cameras, due to ease of review and processing of captured images in related devices such as computers.
Generally, digital cameras provide an auto-focus (AF) capability. FIG. 1 shows a relationship between an anti-dazzling screen and a sensor for conventional auto-focusing procedures. Conventionally, since the position of the AF lens cannot be initially determined, sensor Pl must first optically home in to a mechanism origin (P1 or P2), such as the near end (NEAR) or the infinite far end (∞). Then, the auto-focusing procedure is performed. When the sensor Pl moves within a focus range, the sensor Pl generates high and low signals based on the design of the anti-dazzling screen S. When the sensor Pl is at a covered sub-area such as S1 of the anti-dazzling screen S, the sensor Pl detects and generates low signals. When the sensor Pl is at an uncovered sub-area such as S2 of the anti-dazzling screen S, the sensor Pl detects and generates high signals.
Conventionally, the lengths of the respective covered and uncovered sub-areas are the same. When digital cameras boot or reset, the sensor Pl will first home in to the mechanism origin (P1 or P2) to ensure the starting position of the sensor Pl. This takes time.
Meanwhile, if the sensor Pl is out of control during auto-focus, the auto-focusing procedure may fail. Additionally, if the sensor Pl homes in to an origin beyond the range of the anti-dazzling screen S, the digital camera will crash due to no detection of the anti-dazzling screen S. Further, if the digital camera system crashes or the drive mechanism malfunctions, the sensor Pl will first home in to the mechanism origin (P1 or P2) to re-ensure the starting position of the sensor Pl. The homing of the sensor Pl is time-consuming.